Celebs react to Boston Marathon explosions

New Kids On The Block member and Boston-native, Joey McIntyre was actually an eyewitness at the scene, as he was a participant in the marathon and had just crossed the finish line at the time of the explosions. Joey tweeted that he was okay. His bandmate Donnie Wahlberg also took to Twitter to let fans know he was fine, adding he had "no words to describe the pain" in seeing his city "torn apart this way."

Justin Timberlake sent his thoughts and prayers out to everyone affected by the "terrible incident," as did Britney Spears, Pink, Phillip Phillips, Chris Brown, and the Jonas Brothers. Justin Bieber also gave Boston a shoutout while on tour in Europe. Alicia Keys said she was "shaken" after hearing the news. Ciara also tweeted that she had planned to make some "exciting announcements" today, but that there's no way she would do so "during a time like this."

Kelly Rowland, Lindsay Lohan, Avril Lavigne, Lea Michele and Jordin Sparks also shared sentiments. A number of non-U.S. based artists also reached out to the victims of the Boston tragedy including Victoria Beckham, Ed Sheeran, Ellie Goulding, Simon Cowell, Rita Ora, Jessie J, Olly Murs, Cher Lloyd, The Saturdays, One Direction's Harry Styles and Louis Tomlinson and the Wanted's Max George and Nathan Sykes.

See how the stars are reacting to the tragedy:

There was an explosion by the finish line about 5 minutes after I finished- I'm ok but I'm sure there are many hurt.